Polymer nanocomposite blends

ABSTRACT

Polymer nanocomposite blends of at least two polymers and nanodispersed delaminated phyllosilicates and methods for their production. The polymer nanocomposite blends contain: a) polyamide (PA) from 55 to 95 percent by weight, b) polypropylene (PP) from 4 to 40 percent by weight, c) nanodisperse phyllosilicates from 1 to 9 percent by weight, d) up to 10% by wt. carboxylated polyolefins, particularly copolymers of ethylene with unsaturated carboxylic acids, so that the weight ratios of the compositions always add up to 100 percent by weight. Common stabilizers and fillers may be contained as additives.

The invention relates to polymer nanocomposite blends of at least twopolymers and nanodispersed delaminated phyllosilicates. Thephyllosilicate is a modified natural sodium montmorillonite, hectorite,bentonite, or synthetic mica. The invention also relates to a method ofproducing these nanocomposites and their use. It is the object of thisinvention to produce cost-efficient nanocomposites on polyamide basiswith improved properties such as high rigidity even in their conditionedstate and resistance to thermal oxidation.

Nanocomposites on polyamide as well as polyolefin basis are becomingmore and more attractive compared to conventional composites with glasfilms and minerals respectively with a similar property profile becausethey help reduce weight. Composites of this type are seen as materialsfor injection-molded parts with widespread uses in vehicle and aircraftconstruction, electrical and electronic engineering, equipment andmedical engineering.

Property improvement is mainly due to the capability of thephyllosilicate layers to expand (intercalate) or to completely separatefrom each other (exfoliation). This creates an enlarged surface of thefiller material and an enlarged boundary surface with the matrixpolymer. To achieve intercalation or exfoliation when producing polymernanocomposites, the phyllosilicates are modified by cation exchange withorganic compounds and thus made organophilic. They are also referred toas organoclays. In addition interactions or interfaces with the matrixpolymer are required.

Working organically intercalated phyllosilicates into polymers byin-situ polymerization or melt compounding has been described in severalpatent documents and is mostly associated with an improvement of themechanical and barrier properties as well as thermostability [U.S. Pat.No. 4,739,007, WO0034180].

The in-situ polymerization of ε-caprolactam in the presence oforganophilically modified clay has been described as early as in 1988[U.S. Pat. No. 4,739,007]. Working organoclays into polyethyleneterephthalate (PET) by melt compounding resulted in an improved barrieragainst oxygen [WO 0034180].

Polyamide nanocomposites with a second polymer component are also knownin principle. Working brominated rubber [U.S. Pat. No. 6,060,549] orpolypropylenes grafted with maleic anhydride [X. Liu et al. Polymer 42,2001, pp. 8235-8239] into in-situ polymerized polyamide6/Na-montmorillonite-nanocomposites resulted in improved impact strengthbut reduced mechanical strength of the polyamide. Another finding wasreduced water absorption depending on the PP-g portion in the mixture.

Polyamide composites with an increased flexural modulus and dimensionalstability during water absorption but having the disadvantage of reducedstrength have also been described [EP1076077]. The composites werecompounded in the melt with twin-screw extruders and contain 2 to 40percent by weight of ethylene butylacrylate grafted with maleicanhydride or of polypropylene grafted with maleic anhydride and 0.3 to30 percent by weight of synthetic phyllosilicate modified with triazine.

EP0352042 also describes polyamide nanocomposites with one or twopolymer components. For example, a polyamide nanocomposite preparedin-situ by melt compounding was modified with an ethylene methacrylateZn⁺ ionomer to resist impact. But losses in stability and rigidity weredetected.

In-situ polymerized polyamide 6 nanocomposites that were compounded inthe melt with a modifier for impact resistance (butyl acrylate, methylacrylate rubber or mixtures thereof) are described in DE19854170. Theauthors also claim in-situ polymerization of PA 6 in the presence oforganic phyllosilicates and the synthetic rubber component. Thesecomposites had a clay content of 3.7 percent by weight, rubber contentof 3 percent by weight and a very high modulus of elasticity (5420 MPa),good impact resistance (Charpy 1eU 112 kJ/m² but a low breakingelongation of 2.9%. The phyllosilicates used were modified withdi-2-hydroxyethylmethyl stearyl amine.

Patent document U.S. Pat. No. 5,206,284 claims polypropylene compoundsthat contain a modified PP (PP-g-MA), a polyamide nano-composite (MPA)prepared in situ with 2% organoclay (montmorillonite modified withaminododecaic acid), an ethylene-alpha-olefin rubber or a modifiedethylene-alpha-olefin copolymer such as EPR-g-MA or SEBS-g-MA. ThePP-g-MA/PP/MPA composite at a 30/10/60 weight ratio had a flexuralmodulus of 26000 kg/cm² (2550 MPa), bending strength of 770 kg/cm² (75MPa), yield stress of 450 kg/cm² (45 MPa) and thermostability—HDT@0.45MPa of 150° C. Stability, rigidity, and strength declined when the PPportion was increased.

JP10279752 claims a composition consisting of 40 to 99.9 percent byweight polyolefin grafted with carboxylic acid or anhydride, 0.5 to 40percent by weight polyamide, and 0.01 to 20 percent by weightphyllosilicate with an improved oxygen barrier.

Tjong, S. C.; Meng, Y. Z.; Xu, Y., [J. Applied Polymer Science (2002),86(9), pp. 2330-2337] described a clay modification process by maleicanhydride for producing PA 6/PP-vermiculite nanocomposites. PP andmaleinated vermiculite were first compounded in the melt, and themixture was subsequently processed by injection molding together with PA6. An increase in the tensile modulus from 995 MPa for pure PA 6 to 1397MPa in the nanocomposite having a PP/vermiculite content of 31 percentby weight (8% vermiculite) was observed, with strength having remainedunchanged and elongation having declined strongly.

Hua Wang et al. [“Processing and Properties of PolymericNano-Composites” Polym. Eng. Sci. 41, 11(2001), pp. 2036-2046] studiednylon 6/PP blends to which approx. 10 percent by weight of clay wereadded. Refinement of the blend morphology by adding phyllosilicates wasobserved using a scanning electron microscope. It was found that themodulus of elasticity had increased, which is due to the high claycontent, and dramatically reduced strength. Compatibilization withPP-g-MA resulted in a drop in rigidity and had little or no positiveeffect on strength.

Polyamides fulfil high-quality functions as fibers, foils or componentsin the wider sense of the term. As they tend to absorb water, extensionof their applicability is limited. For example, PA 6 absorbs 3% of waterat 23° C. and 50% humidity, and up to 9.5% at 100% relative humidity.The intercalated water is known to influence basic mechanical parametersconsiderably.

It is known that water absorption can be reduced in blends of polyamideand polyolefins depending on polyolefin content [L. Bottenbruch, R.Binsack; Kunststoffhandbuch; Carl Hanser Verlag, München 1998]. It istherefore usually inevitable to perform a compatibilization usingfunctionalized polyolefins such as block or graft copolymers and theassociated influencing of interfacial adhesion.

But this procedure has its setbacks. Using compatibilizers such asfunctionalized polyolefins and copolymers mostly has a softening effectand results in reduced strength and rigidity.

Polyamides are also sensitive to high working temperatures. It is knownthat polyamides suffer thermooxidative damage if stored at airtemperatures even below their melting point. The polyamides lose theirphysical properties depending on storage time and temperature. Thisphenomenon is known as oven aging and is not related to thermaldegradation that can occur at temperatures above the melting point. Theproperty of polymers to maintain their mechanical strength, toughness,etc. for longer periods of time is called thermostability which we stillcall thermal or thermooxidative stability in this document. Heatstabilizers, glass fibers, and other polymers such as polyphenyleneether to improve the thermal stability of polyamides.

The most common methods used to determine thermal properties such as HDT(heat deflection temperature) or DMTA (dynamic mechanical thermalanalysis) primarily provide information about short-term stability ofmaterials at high temperatures. The time-dependent influence of thermaloxidation and the associated deterioration of properties cannot bedetermined satisfactorily in this way. A statement on the thermalstability of polyamide nanocomposites has been based on an HDT increaseor the storage modulus at the respective temperature or a glasstransition temperature shift (DMTA measurement).

The studies performed on long-term stability revealed that polyamide6/clay nanocomposites show no thermostability in air at temperaturesover 100° C. Thermal oxidation on the surface of the nanocomposite ismuch faster than that of the polyamide itself, which results in adramatic drop in strength and damages the surface quality (see theproperties of PA nanocomposites listed in Table 4).

It is the object of this invention to maintain the favorable propertiesof polyamide such as rigidity in its conditioned state and to achievegood thermooxidative stability in conjunction with reduced density ascompared to conventional reinforcement of glass or minerals and toreduce costs as compared to pure PA 6/clay nanocomposites.

According to the invention, this object is surprisingly achieved bypolymer nanocomposite blends containing

-   a) polyamide (PA) from 55 to 95 percent by weight,-   b) polypropylene (PP) from 4 to 40 percent by weight,-   c) nanodisperse phyllosilicates from 1 to 9 percent by weight, and-   d) (optionally) up to 10 percent by weight, preferably from 0.1 to    1.9 percent by weight of carboxylated polyolefins, in particular    copolymers of ethylene with unsaturated carboxylic acids    so that the weight ratios of the compositions always add up to 100    percent by weight. Common stabilizers and fillers may be contained    as additives.    Component a) Polyamide

Polyamides are produced by a condensation reaction of lactamen with aring that has more than three members and/or ω-amino acid(s) or at leastone diacid and at least one diamine. The polyamide resins produced bypolycondensation are polyamide polymers or copolymers. The polyamideresin is selected from the group consisting of homopolyamides,copolyamides and mixtures thereof, and these polyamides are eithersemicrystalline or amorphous.

Examples of monomers include α-caprolactam, α-aminocaproic acid,11-aminoundecanoic acid, 9-aminononanoic acid, and α-piperidone.Examples of diacids include adipic acid, sebacic acid, dodecanoicdiacid, glutaric acid, terephthalic acid, 2-methyl terephthalic acid,isophthalic acid, naphtaline dicarboxylic acid. Examples of diaminesinclude tetramethylene diamine, hexamethylene diamine, nonamethylenediamine, decamethylene diamine, undecamethylene diamine, dodecamethylenediamine, p-aminoaniline, and m-xyloldiamine.

The polyamides are preferably selected from the group consisting ofpolyamide (nylon) 6 or polyamide (nylon) 6/66 with a content of 0 to 20%polyhexamethylene adipamide.

A polyamide 6 with a solution viscosity of 2.2 to 4.0 preferably 2.4 to3.5, measured in a 1% solution of 96% sulfuric acid at 23° C., isparticularly suited for the polymer nanocomposite blends of theinvention.

Component b) Polypropylene

Homopolymers or statistical copolymers or block copolymers of propylenewith one or several olefins such as ethylene and linear and/or branchedC₄ to C₁₀ 1-olefins are used as polypropylenes. It is practical to usepoly-propylene homopolymers and block copolymers with a low ethylenecontent.

The preferred component b) is a polypropylene with a melt-flow indexfrom 1 to 110, from 5 to 30 ccm/10 min (230° C./2.16 kg).

Component c) Nanodisperse Phyllosilicates

The preferred nanodisperse phyllosilicate is a natural sodiummontmorillonite, hectorite, bentonite, or synthetic mica with a cationexchange capacity of 60 to 150 mval/100 g.

It is preferred to use up to 5 percent by weight of phyllosilicates.Compared to Hua Wang et al., these composites are characterized by greatstrength and rigidity in the freshly molded and conditioned states,reduced water absorption, and improved thermooxidative stability.

Two phases coexist in the nanocomposite blends according to theinvention so that the organically intercalated phyllosilicates primarilydisperse or exfoliate in the polyamide phase. Accumulation of theexfoliated layers at the boundary surface with the polypropylene phasewas not observed using transmission electron microscopy (TEM) (FIG. 4).It is assumed that interaction between the polyamide and polypropylenephases is initiated by the intercalated and delaminated phyllosilicates.

A delaminated phyllosilicate (nanoclay, organically intercalated) in themeaning of this invention are swellable phyllosilicates in which thespacings between the silicate layers were enlarged by reaction withhydro-phobing agents. For montmorillonite, intercalation with suitable,preferably cationic intercalation components results in a layer spacingfrom 1.2 to 5.0 nm.

Phyllosilicates with a cation exchange capacity of at least 50,preferably 60 to 150 mval/100 g are preferred. The alkaline or earthalkaline metals that can be exchanged in these swellable phyllosilicatesare replaced fully or in part by onium, ammonium, phosphonium, orsulfonium ions in an ion exchange reaction. Swellable phyllosilicates inwhich 50 to 200% of the replaceable inorganic cations are replaced byorganic cations are particularly preferred.

Cationic nitrogen compounds suitable for intercalation are alkylammoniumions such as lauryl ammonium, myristyl ammonium, palmityl ammonium.Other preferred cationic nitrogen compounds are quaternary ammoniumcompounds such as distearyldimethyl ammoniumchloride anddimethyldistearylbenzyl ammoniumchloride.

Suitable bifunctional cationic nitrogen molecules include, first of all,ω-aminocarboxylic acids such as ω-aminoundecanoic acid,ω-aminododecanoic acid, ω-aminocaprylic acid, or ω-aminocaproic acid.

Other preferred nitrogen-containing intercalation components arecaprolactam, lauryllactam, melamine, and oligomeric water-solubleamides.

It is preferred that all nitrogen-containing intercalation componentsare used in protonated form. All water-soluble organic and inorganicacids are suitable for protonation. Mineral acids such as hydrochloricacid, sulfuric acid, nitric acid and phosphoric acid, as well as aceticacid, formic acid, oxalic acid, and citric acid. Examples of suitablephosphonium ions include docosyl trimethyl phosphonium, hexatriacontyltricyclohexyl phosphonium, octadecyl triethyl phosphonium, dicosyltriisobutyl phosphonium, methyltrinonyl phosphonium, ethyltrihexadecylphosphonium, di-methyldidecyl phosphonium, diethyldioctadecylphosphonium, octadecyl diethylallyl phosphonium, trioctylvinylbenzylphosphonium, dioctydecylethyl hydroxyethyl phosphonium, docosyldiethyldichlorobenzyl phosphonium, octylnonyldecylpropargyl phosphonium,triisobutyl perfluorodecyl phosphonium, eicosyltrihydroxymethylphosphonium, triacontyltriscyanethyl phosphonium, andbistrioctylethylene diphosphonium.

Component d) Carboxylated Polyolefins

Suitable components D are polyolefins, particularly polyolefincopolymers that are functionalized with unsaturated mono/ ordicarboxylic acids or anhydrides.

They can be contained in the nanocomposite blends at up to 10 percent byweight, preferably at 0.1 to 1.9 percent by weight. Particularly suitedare ethylene-ionomer copolymers, preferably ethylene acrylic acid orethylene methacrylic acid copolymers that are fully or partlyneutralized with metal ions. The ethylene ionomer can be a metal ioncontaining ethylene butadiene acrylic acid copolymer, ethylenemethylacrylate maleic acid copolymer. The preferred metal ion is a Zn+,Na+, Mg+, or Zn-amine complex ion.

Other Additives

The polymer nanocomposite blends according to the invention mayoptionally contain common stabilizers and fillers selected from thegroups of oxidation stabilizers, light stabilizers, process stabilizers,UV stabilizers, sliding agents, separating agents, pigments, dyes, flameretardants, fiber reinforcing fillers.

Examples of oxidation and process stabilizers are mixtures of at leasttwo substances selected from the groups of metal halogenides such assodium, potassium, lithium, zinc, and copper halogenides or organiccompounds on phenol basis, hydroquinones, organic phosphite compounds.

Examples of UV stabilizers are resorcinols, salicylates, hinderedamines, benzotriazoles and benzophenols.

Examples of sliding and separating agents include stearic acid, stearinalcohol, stearic acid amide, waxes, carboxylic acid esters, metal saltsof carboxylic acid.

Examples of pigments are titane dioxide, cadmium sulfide, cadmiumselenite, ultramarine blue, black.

An example of an organic dye is nigrosine.

Examples of flame retardants include organic halogen compounds, organicphosphor compounds, red phosphor, metal hydroxides.

Examples of fillers and reinforcing agents include glass fibers, glasspearls, glass flakes, talc, carbon fibers, kaolin, wollastonite,molybdenum sulfide, potassium titanate, barium sulfate, electroconduciveblack and aramide fibers.

In addition, other additives such as magnetizing substances, EMI maskingagents, antibacterial and antistatic agents may be introduced.

The polymer nanocomposite blends are produced in that the componentscontain

-   a) polyamide (PA) from 55 to 95 percent by weight,-   b) polypropylene (PP) from 4 to 40 percent by weight,-   c) nanodisperse phyllosilicates from 1 to 9 percent by weight, and-   d) up to 10 percent by weight, preferably from 0.1 to 1.9 percent by    weight of carboxylated polyolefins, in particular copolymers of    ethylene with unsaturated carboxylic acids    and may additionally contain common stabilizers and fillers in    excess of this composition of a total of 100 percent by weight and    are compounded at temperatures above the melting points of the    polymers involved in an extruder or kneader.

A variant of this process is to compound the components in one step.

Two-step methods are conceivable as well.

Components c) and d) can first worked into parts of component a) to forma master batch which is compounded in a second step with component b)and the remaining quantity of component a) and processed further.

In another embodiment, components d) and b) are first compounded in anextruder or kneader at temperatures above the melting points of thepolymers involved to become a modified polypropylene, then component, apart of component a) is worked in to form a master batch which in a nextstep is compounded with the modified polypropylene and the remainingquantity of component a) and then processed further.

Another option is to compound components d) and b) in an extruder orkneader at temperatures above the melting points of the polymersinvolved to become a modified polypropylene and in a next step tocompound the modified polypropylene with component a) and component d)and to continue processing.

The polymer nanocomposite blends according to the invention areparticularly suited for use as extrudates, injection-molded parts, orfibers.

The intercalation components mentioned in the description of componentc) act as hydrophobing agents and influence the surface tension of thephyllosilicates so that polarity and the overall surface energy valuedrop. Polarity and surface tension of the polyamide drop aftercompounding with polyamide. This ensures better intermixing and finerdispersion of the polypropylene phase in the nanocomposite blends ascompared to pure PA 6/PP nanocomposite blends.

The TEM examination of the PA 6/PP nanocomposite blends according to theinvention shows fine dispersion of the polypropylene phase. Theparticles have a size between 0.1 and 1 μm (FIG. 4 a). FIG. 4 b showsthat the exfoliated phyllosilicates are mainly dispersed inside thepolyamide matrix, and accumulation of the layers that form some kind ofa card structure around the polypropylene particles is clearly visible.Increased concentration of the organophilic phyllosilicate at theboundary surface of the polyamide and polypropylene phases lowers thesurface tension difference between the normally incompatible polymers.

We also studied the morphology in the nanocomposite blends (ongold-plated cryofracture surfaces) with a scanning electron microscope(SEM). Larger structures were observed. The PP phase is distributed inthe form of sticks in the PA/PP nanocomposite blends (FIG. 5 a). Afteradding only 1 to 1.9% by wt. ethylene ionomer, it is no longer possibleto distinguish the PP phase from the PA phase. The cryofracture surfaceappears as a solid surface with an uninterrupted PA/clay-PP boundarysurface. The figure shows small PP particles embedded in thepolyamide/clay matrix with a diameter less than 1 μm (FIG. 5 b).

The nanocomposite blends according to the invention have excellentmechanical properties such as strength, rigidity, and notch-impactresistance in freshly molded and conditioned states as well as afterstorage at air temperature.

Compared to pure polyamide, the tensile modulus of elasticity isincreased by up to 50% in the freshly molded state, and the increase canbe up to 150% in the conditioned state. If compared to apolyamide/polypropylene blend of the respective composition, theincrease is up to 70% in the freshly molded and up to 75% in theconditioned state. Water absorption of the described PA/PP nanocompositeblends after conditioning (typically at 23° C. and 95% humidity) isclearly below the value of the pure nanocomposite and the pure polyamide6. The nanocomposite blends also show improved tensile moduli ofelasticity by 150% as compared to pure polyamide in the saturated stateand after being stored in water for more than 1800 hours.

After storage at temperatures above 100° C. (110, 120, 130 and 150° C.),the nanocomposite blends according to the invention show the slightestloss in strength.

The nanocomposite blends according to the invention show a clearlyreduced loss in mechanical strength after temperature storage at 150° C.after adding small quantities of ethylene ionomer, particularly up to1.9 percent by weight, particularly when using a low-molecular ethyleneionomer completely neutralized with Zn and without adding a heatstabilizer.

In addition to thermal stability, reduced water absorption anddistinctively higher rigidity were detected in these nanocompositeblends in their conditioned state in accordance with ISO 1110 (50%relative humidity).

The storage modulus, as measured in a torsion test, of the nanocompositeblends according to the invention with 15 percent by weight of PP issimilar to the one for PA 6 nanocomposite at a temperature range from 25to 150° C. and is up to 100% higher at a temperature of 100° C. thanthat of pure polyamide 6 (FIG. 6). A slight decline of the storagemodulus in the n nanocomposite blends according to the invention isfound with increasing PP content but it remains above the storagemodulus of pure polyamide 6 (FIG. 7).

The invention is explained in greater detail with reference to theexamples below, to which however it is not limited:

EXAMPLES 1 TO 7 One-Step Method

PA/PP nanocomposite blends were produced at a L/D ratio of at least 40using a twin-screw extruder (ZSK 25, Coperion Werner & Pfleiderer). Thepolymers and phyllosilicates intercalated with organic substances wereadded in the first zone using polymer or powder scales. The batch wascompounded at temperatures from 220 to 260° C. and a speed of 400 min⁻¹.The compounded nanocomposite blends were made into test specimens usinginjection molders (Arburg Allrounder 320M 850-210).

The spacing between the silicate sheets was determined by WAXS analyses(WAXS=wide angle X-ray scattering). Based on this and on TEM recordings,conclusions were drawn regarding the degree of exfoliation or dispersionof the phyllosilicates. The distribution of polypropylene phase in thenanocomposite blends was evaluated based on TEM and SEM recordings.

(TEM=Transmission Electron Microscopy; SEM=Scanning Electron Microscopy)

The volumetric melt-flow indices of the parent components and of thenanocomposite blends were measured with a melt-flow index tester (byGöttfert) and listed as melt-flow indices with the examples.

The mechanical properties of the nanocomposite blends were tested in thefreshly molded and conditioned states using a tensile test according toDIN EN ISO 527 and notch-impact strength test according to DIN EN ISO179/1eA. Thermostability (HDT) was measured according to ASTM D648. Thesamples in examples 1 to 4 were conditioned at a temperature of 23° C.and a humidity of 95% for a period of 280 hours (conditioning 1). Thensome of the samples were tested in the tensile test while the rest wasstored in water at room temperature until saturation was reached(conditioning 2). The composition of the nanocomposite blends is shownfor each example. The properties are listed in Tables 1 to 4, waterabsorption is shown in FIGS. 1, 2, and the moduli of elasticity areshown in FIG. 3.

The dynamic-mechanical behavior of the nanocomposite blends in Examples6 and 7 was tested using a RDA II torsion test device (by RheometricScientific) at a constant elongation of 0.1% and a frequency of 1 Hz.The storage modulus as a function of temperature is shown in FIG. 6.

Samples 6 and 7 were conditioned according to EN ISO 1110 at 70° C. and62% relative humidity until their weight remained constant. The testrods of the samples in Examples 6 and 7 were also stored in circulatingair ovens at 110° C., 120° C., 130° C., and 150° C. and subsequentlytested for tensile properties.

The solution viscosity of polyamide 6 was measured in a 1% solution insulfuric acid (96%) at 25° C.

EXAMPLE 1

Polyamide 6 with a melt-flow index of 4.9(230° C./2.16 kg) and arelative solution viscosity of 3.45 (reference polyamide I),polypropylene with a melt-flow index of 5(230° C./2.16 kg), andoctadecylamine-modified montmorillonite (such as Nanofil 848) werecompounded at a weight ratio of 80/15/5.

EXAMPLE 2

Polyamide 6 with a melt-flow index of 4.9(230° C./2.16 kg) and arelative solution viscosity of 3.45, polypropylene with a melt-flowindex of 5(230° C./2.16 kg), and octadecylamine-modified montmorillonite(such as Nanofil 848) and aminododecanic acid-modified montmorillonite(such as Nanofil 784) were compounded at a weight ratio of79.2/15.8/2.5/2.5.

REFERENCE EXAMPLE 3

Polyamide 6 with a melt-flow index of 4.9(230° C./2.16 kg) and arelative solution viscosity of 3.45, polypropylene with a melt-flowindex of 5(230° C./2.16 kg) were compounded at a weight ratio of 85/15.

REFERENCE EXAMPLE 4

Polyamide 6 with a melt-flow index of 4.9(230° C./2.16 kg) and arelative solution viscosity of 3.45, and octadecylamine-modifiedmontmorillonite (such as Nanofil 848) were compounded at a weight ratioof 96.8/3.2.

The results are shown in the tables below. TABLE 1 Properties of thenanocomposite blends of the invention Reference Example 1 Example 2 Ref.Ex. 3 Ref. Ex. 4 polyamide I Clay 5 5 — 3.2 — content in % E modulus4348 4036 2786 4392 3180 in MPa HDT/A 100 103 54.3 104 68 ASTM D648 @1.8MPa in ° C.

TABLE 2 Properties of the nanocomposite blends of the invention afterconditioning at 23° C. and 95% relative humidity for a period of 280hours Ref. Reference Example 1 Example 2 Ref. Ex. 3 Ex. 4 polyamide IClay content 5 5 — 3.2 — in % E modulus 3077 2725 1941 2249 1516 in MPaWater 1.18 1.15 1.29 1.68 2.22 absorption in %

TABLE 3 Water absorption of the nanocomposite blends of the inventionafter conditioning at 23° C. in water. Ref. Reference Example 1 Example2 Ref. Ex. 3 Ex. 4 polyamide I Clay content 5 5 — 3.2 — in % Water 7.77.7 7.8 8.4 9.4 absorption in %

EXAMPLE 5

Polyamide 6 with a melt-flow index of 22.3(230° C./2.16 kg) and arelative solution viscosity of 2.7 (reference polyamide II),polypropylene with a melt-flow index of 24(230° C./2.16 kg), andoctadecylamine-modified montmorillonite (such as Nanofil 848) werecompounded at a weight ratio of 80/15/5. The PA 6/PP nanocomposite blendshowed improved mechanical and thermal properties, an E modulus increaseof 43% and HDT increase of 73%. Blend properties: E modulus: 3860 MPaHDT (1.8 MPa): 95° C. Properties of the E modulus: 2700 MPa ref.Polyamide II: HDT (1.8 MPa): 55° C.

REFERENCE EXAMPLE 6

Polyamide 6 with a melt-flow index of 6.6(230° C./2.16 kg) and arelative solution viscosity of 3.2 (reference polyamide III), andoctadecylamine-modified montmorillonite (such as Nanofil 848) werecompounded at a weight ratio of 95/5. 0.2% of Irganox B1171 (a blend ofheat and process stabilizers) were added to the mixture.

REFERENCE EXAMPLE 7

Polyamide 6 with a melt-flow index 6.6(230° C./2.16 kg) and relativesolution viscosity of 3.2 (reference polyamide III) was processed whileadding 0.2% Irganox B1171 (a blend of heat and process stabilizers).TABLE 4 Properties of PA/PP nanocomposite blends Reference Ref. Example6 Ref. Example 7 Example 8 Example 10 Example 12 Example 14 polyamideIII PA 6, % by wt. 94.8 99.8 80 79 78.2 78.2 100 PP, % by wt. — — 15 1515 15 — Clay content, % by wt. 5 — 5 5 5 5 — Ionomer Ac, % by wt. — — —1 — — Ionomer Ac1, % by wt. — — — — 1.8 — Ionomer Sr, % by wt. — — — — —1.8 — Irganox, % by wt. 0.2 0.2 — — — — — MVI (230° C./2.16 kg), 3.6 6.62.8 1.6 2.4 1.5 6.6 cm³/10 min Tensile strength, MPa 92.9 79 73 72 75 7679 Retention of tensile strength 16.7 27.5 30 52 45 48 <25 after 336hours at 150° C., % Tensile elongation, % 3.5 3.8 3.1 3.2 3.2 3.5 4.2Breaking elongation, % 4.6 6 4.6 6 29.5 E modulus, MPa 4140 3034 39053810 3580 3570 2720 Notch-impact strength, 4 3.67 4 4.2 4 4.3 2.5 23°C., kJ/m² Water absorption acc. to EN 2.4 2.5 1.9 1.8 2.1 2.1 2.5 ISO1110, (50%/RH), % E modulus, (50% RH) MPa 1760 936 1900 1920 1740 1670930

EXAMPLES 8 TO 16 Two-Step Method

The PA/PP nanocomposite blends were produced at a L/D ratio of at least40 using a twin-screw extruder (ZSK 25/40, Coperion Werner &Pfleiderer). The polymers and phyllosilicates intercalated with organicsubstances were added in the first zone using polymer or powder scales.The batch was compounded at zone temperatures from 220 to 260° C. and aspeed of 250 and 400 min⁻¹ respectively. First, the master batches PA6/clay without or with ethylene acrylic acid or ethylene methacrylicacid ionomer were prepared. Then the master batches were compounded withPP and PA 6. The overall throughput in master batch production andcompounding was 6 kg/h.

The compounded nanocomposite blends were made into test specimens usinginjection molders (Arburg Allrounder 320M 850-210).

The spacing between the silicate sheets in the master batches wasdetermined by WAXS analyses (WAXS=wide angle X-ray scattering).

The mechanical properties of the nanocomposite blends were tested (infreshly molded and conditioned states) using a tensile test according toDIN EN ISO 527 and notch-impact strength test according to DIN EN ISO179/1eA.

The dynamic-mechanical behavior of the nanocomposite blends was testedusing a RDA II torsion test device (by Rheometrics) at a constantelongation of 0.1% and a frequency of 1 Hz. The composition of thenanocomposite blends is shown in the examples below and listed in Tables4 and 5, the storage modulus as a function of temperature is shown inFIG. 7.

The samples used in Examples 8 and 16 were conditioned according to ENISO 1110 at 70° C. and 62% relative humidity until their weight remainedconstant. Test rods of samples 10 to 15 were stored in the circulatingair oven at 150° C. and subsequently subjected to a tensile test.

The solution viscosity of polyamide 6 was measured in a 1% solution insulfuric acid (96%) at 25° C.

EXAMPLE 8

Polyamide 6 with a melt-flow index of 6.6(230° C./2.16 kg) and arelative solution viscosity of 3.2 (reference polyamide III),polypropylene with a melt-flow index of 6 (230° C./2.16 kg), andoctadecylamine-modified montmorillonite (such as Nanofil 848) were used.

First, a master batch of PA 6 and clay at an 80/20 weight ratio wasprepared. WAXS analyses showed that the spacings between the silicatesheets widened by more than 4.5 nm. The master batch was then compoundedwith PA 6 and PP so that the final concentration of the components inthe PA 6/PP/clay mixture was at a 80/15/5 weight ratio.

EXAMPLE 9

The same procedures and materials as in Example 10 were used. The finalconcentration of the components in the PA 6/PP/clay mixture was at aweight ratio of 70/25/5.

EXAMPLE 10

Polyamide 6 with a melt-flow index of 6.6(230° C./2.16 kg) and arelative solution viscosity of 3.2 (reference polyamide III),polypropylene with a melt-flow index of 6 (230° C./2.16 kg), alow-molecular ethylene acrylic acid copolymer (such as Aclyn 295)completely neutralized with Zn (here called ionomer Ac) andoctadecylamine-modified montmorillonite (such as Nanofil 848) were used.

First, a master batch of PA 6, ionomer Ac, and clay at a 75/5/20 weightratio was prepared. WAXS analyses showed that the spacings between thesilicate sheets widened by more than 4.26 nm. The master batch was thencompounded with PA 6 and PP so that the final concentration of thecomponents in the PA 6/PP/ionomer Ac/clay mixture was at a 79/15/1/5weight ratio.

EXAMPLE 11

The same procedures and materials as in Example 12 were used. The finalconcentration of the components in the PA 6/PP/ionomer Ac/clay mixturewas at a weight ratio of 69/25/1/5.

EXAMPLE 12

Polyamide 6 with a melt-flow index of 6.6(230° C./2.16 kg) and arelative solution viscosity of 3.2 (reference polyamide III),polypropylene with a melt-flow index of 6 (230° C./2.16 kg), alow-molecular ethylene acrylic acid copolymer (such as Aclyn 291) partlyneutralized with Zn (here called ionomer Ac1) andoctadecylamine-modified montmorillonite (such as Nanofil 848) were used.

First, a master batch of PA 6, ionomer Ac1, and clay at a 72.5/7.5/20weight ratio was prepared. WAXS analyses showed that the spacingsbetween the silicate sheets widened by more than 4.26 nm. The masterbatch was then compounded with PA 6 and PP so that the finalconcentration of the components in the PA 6/PP/ionomer Ac1/clay mixturewas at a 78.2/15/1.8/5 weight ratio.

EXAMPLE 13

The same procedures and materials as in Example 14 were used. The finalconcentration of the components in the PA 6/PP/ionomer Ac1/clay mixturewas at a weight ratio of 69.5/25/1.5/4.

EXAMPLE 14

Polyamide 6 with a melt-flow index of 6.6(230° C./2.16 kg) and arelative solution viscosity of 3.2 (reference polyamide III),polypropylene with a melt-flow index of 6 (230° C./2.16 kg), ahigh-molecular ethylene methacrylic acid copolymer (such as Surlyn)partly neutralized with Zn (here called ionomer Sr) andoctadecylamine-modified montmorillonite (such as Nanofil 848) were used.

First, a master batch of PA 6, ionomer Sr, and clay at a 72.5/7.5/20weight ratio was prepared. WAXS analyses showed that the spacingsbetween the silicate sheets widened by more than 4.3 nm. The masterbatch was then compounded with PA 6 and PP so that the finalconcentration of the components in the PA 6/PP/ionomer Sr/clay mixturewas at a 78.2/15/1.8/5 weight ratio.

EXAMPLE 15

The same procedures and materials as in Example 16 were used. The finalconcentration of the components in the PA 6/PP/ionomer Sr/clay mixturewas at a weight ratio of 69.5/25/1.5/4.

EXAMPLE 16

The same procedures and materials as in Example 16 were used. The finalconcentration of the components in the PA 6/PP/ionomer Sr/clay mixturewas at a weight ratio of 55.9/40/1.1/3. TABLE 5 Properties of PA/PPnanocomposite blends Example Example Example Example 9 11 13 15 Example16 PA 6, % by wt. 69 69.5 69.5 55.9 PP content, 25 25 25 25 40 % by wt.Clay content, 5 5 4 4 3 % by wt. Ionomer Ac, — 1 — — — % by wt. IonomerAc1, — — 1.5 — — % by wt. Ionomer Sr, — — — 1.5 1.1 % by wt. MVI (230°C./2.16 kg), 2.6 1.4 2.8 1.5 2.7 cm³/10 min Tensile strength, 63 63 6467 57 MPa Retention of 55 83 80 58 63 tensile strength after 336 hoursat 150° C., % Tensile elongation, % 2.9 3.2 2.9 3.4 3.8 Breaking 4 5 3.45.3 4.3 elongation, % E modulus, MPa 3500 3100 3311 3190 2870Notch-impact 3.4 4.2 4.2 3.8 5.2 strength, 23° C., kJ/m² Waterabsorption 1.5 1.36 2 2 1.44 acc. to EN ISO 1110, (50%/RH), % E modulus,1980 2070 1750 1670 1640 (50% RH) MPaFIGS. 1 to 7

-   FIG. 1: Water absorption of the nanocomposite blends at 23° C. and    95% relative humidity as a function of storage time-   FIG. 2: Water absorption of the nanocomposite blends at 23° C. in    water as a function of storage time-   FIG. 3: E moduli of the nanocomposite blends in freshly molded and    conditioned states (23° C./95% relative humidity—after 280 hours;    23°/in water after 1800 hours and after 4000 hours)-   FIG. 4: TEM recording of ultrathin slices of PA 6/PP nanocomposite    blends: a) contrasted, b) uncontrasted-   FIG. 5: SEM recordings of cryofracture surfaces of the test rods of    PA 6/PP nanocomposite blends: a) without additional    compatibilization, b) with 1.8% by wt.    ethylene ionomer copolymer-   FIG. 6: Storage modulus of PA/PP nanocomposite blends according to    the invention as a function of temperature-   FIG. 7: Storage modulus of PA/PP nanocomposite blends according to    the invention as a function of temperature

1.-10. (canceled)
 11. Nanocomposite blends containing a) polyamide (PA)from 55 to 95% by wt., b) polypropylene (PP) from 4 to 40% by wt., c)nanodisperse phyllosilicates from 1 to 9% by wt. selected from the groupof natural sodium montmorillonite, hectorite, bentonite, or syntheticmica modified with onium ions and having a cation exchange capacity or60 to 150 mval/100 g, d) polyolefin copolymers, especially copolymers ofethylene with unsaturated carboxylic acids, up to 1.9% by wt., that maycontain common stabilizers and fillers in addition to this compositionof 100% by wt. total.
 12. The polymer nanocomposite blends according toclaim 11 wherein component a) is a polyamide 6 with a solution viscosityfrom 2.2 to 4.0, preferably from 2.4 to 3.5, the solution viscositybeing measured in a 1% solution of 96% sulfuric acid at 25° C.
 13. Thepolymer nanocomposite blends according to claim 11 wherein component b)is a polypropylene with a melt-flow index from 1 to 110, preferably from5 to 30 ccm/10 min (230° C./2.16 kg).
 14. The polymer nanocompositeblends according to claim 12 wherein component b) is a polypropylenewith a melt-flow index from 1 to 110, preferably from 5 to 30 ccm/10 min(230° C./2.16 kg).
 15. The polymer nanocomposite blends according toclaim 11 wherein component d) is contained in the nanocomposite blendsat 0.1 to 1.9% by wt. and preferably is an ethylene acrylic acidcopolymer or an ethylene methacrylic acid copolymer that is partly orfully neutralized with metal ions.
 16. The polymer nanocomposite blendsaccording to claim 12 wherein component d) is contained in thenanocomposite blends at 0.1 to 1.9% by wt. and preferably is an ethyleneacrylic acid copolymer or an ethylene methacrylic acid copolymer that ispartly or fully neutralized with metal ions.
 17. The polymernanocomposite blends according to claim 13 wherein component d) iscontained in the nanocomposite blends at 0.1 to 1.9% by wt. andpreferably is an ethylene acrylic acid copolymer or an ethylenemethacrylic acid copolymer that is partly or fully neutralized withmetal ions.
 18. The polymer nanocomposite blends according to claim 14wherein component d) is contained in the nanocomposite blends at 0.1 to1.9% by wt. and preferably is an ethylene acrylic acid copolymer or anethylene methacrylic acid copolymer that is partly or fully neutralizedwith metal ions.
 19. A method for producing polymer nanocomposite blendswherein the components a) polyamide (PA) from 55 to 95% by wt., b)polypropylene (PP) from 4 to 40% by wt., c) nanodisperse phyllosilicatesfrom 1 to 9% by wt. selected from the group of natural sodiummontmorillonite, hectorite, bentonite, or synthetic mica modified withonium ions and having a cation exchange capacity or 60 to 150 mval/100g, d) polyolefin copolymers, especially copolymers of ethylene withunsaturated carboxylic acids, up to 1.9% by wt., that may contain commonstabilizers and fillers in addition to this composition of 100% by wt.total are compounded at temperatures above the melting points of thepolymers involved in an extruder or kneader.
 20. The method according toclaim 19 wherein the components are compounded in one step.
 21. Themethod according to claim 19 wherein components c) and d) are firstworked into parts of component a) to form a master batch which iscompounded in a second step with component b) and the remaining quantityof component a) and then processed further.
 22. The method according toclaim 19 wherein components d) and b) are first compounded in anextruder or kneader at temperatures above the melting points of thepolymers involved and component c) and a part of component a) are workedin to produce a master batch which in a next step is compounded with themodified polypropylene and the remaining quantity of component a) andthen processed further.
 23. The method according to claim 19 whereincomponents d) and b) are compounded in an extruder or kneader attemperatures above the melting points of the polymers involved to becomea modified polypropylene and in a next step this modified polypropylenecompounded with component a) and component d) and then processedfurther.
 24. Use of the nanocomposite blends according to any one ofclaims 11 to 18, produced according to one of claims 19-23, asextrudates, injection-molded parts, or fibers.